The present invention relates generally to a swash plate compressor and, more specifically, to a mechanism for converting the rotation of a swash plate into the reciprocating movement of pistons.
A conventional variable displacement swash plate compressor for compressing refrigerant gas is disclosed, for example, in unexamined Japanese patent application publication No. 8-28447. According to this publication, the compressor has a single-headed piston 22 which is slidably received in each cylinder bore 1a and a pair of spherical shoes 23A, 23B which is fitted in neck portion of the single-headed piston 22. The swash plate 15 has a boss portion formed at its rear face, and a thrust bearing 20 is fitted to the boss portion through the races 20a, 20b on the front and rear sides of the bearing 20, respectively. The race 20a is in contact with the swash plate 15. The swash plate 15 and the thrust bearing 20 are inserted between the shoes 23A, 23B, so that the shoes 23A, 23B are in contact with the swash plate 15 and the race 20b, respectively. The rotation of the swash plate 15 is converted into the reciprocating movement of the single-headed piston 22 through the shoes 23A, 23B and the thrust bearing 20.
In such swash plate compressor, the race 20a adjacent to the swash plate 15 rotates following the rotation of the swash plate 15, but the race 20b adjacent to the shoe 23B hardly follows the rotation of the swash plate 15 because of the rollers 20c. Therefore, the resistance due to the relative displacement between the swash plate 15 and the shoe 23B is provided only by the rolling resistance of the rollers 20c. This rolling resistance is far smaller than the slide resistance produced when the shoe 23B is provided in direct contact with the swash plate 15. This helps improve the compression efficiency by reducing power loss.
Another conventional compressor is disclosed in unexamined Japanese patent application publication No. 2002-5013. The compressor has a drive shaft 21 which is rotatably supported by the housing assembly H and a swash plate 22 which is supported on the drive shaft 21 and accommodated in crank chamber 16 of the compressor. The swash plate 22 has a land portion 23 at its radially inner portion and a peripheral portion 24 having a reduced thickness. This swash plate 22 is operatively connected to the drive shaft 21 through a hinge mechanism 25 and a lug plate 26, so that the swash plate 22 is rotatable with the drive shaft 21 and tiltable with respect to the drive shaft 21 while sliding in the axial direction of the drive shaft 21.
The peripheral portion 24 of the swash plate 22 is slidably held between the pair of shoes 27 and 28 so that the swash plate 22 is operatively connected to each single-headed piston 20. As the swash plate 22 rotates with the drive shaft 21, the rotation of the swash plate 22 is converted into reciprocating movement of each piston 20 for compression of refrigerant gas in a manner that is well known in the art. The swash plate 22 is coated with a film of amorphous hard carbon 43, 44, which is called diamond-like carbon film, at the front and rear surfaces 39, 40 of the entire peripheral portion 24 thereof. The provision of such film protects the slide surfaces between the swash plate 22 and the shoes 27, 28 from abrasion or seizure which may otherwise occur.
According to the swash plate compressor disclosed in the publication No. 8-28447, however, it is difficult for an oil film to be formed on the contact surface between the race 20b and the shoe 23B due to the less relative rotation therebetween in the rotational direction of the swash plate 15. Moreover, small vibration of the swash plate 15 occurring in vertical direction during the compression and suction strokes may cause abrasion or seizure between the race 20b and the shoe 23B despite the provision of the thrust bearing 20.
To solve the problem in the above publication No. 8-28447, it is conceivable that the disclosure of the above publication No. 2002-5013 is applied to the compressor of the publication No. 8-28447 by forming an amorphous hard carbon film having characteristics of low friction and high hardness over the whole surface of the race 20b thereby to improve the sliding condition between the race 20b and the shoe 23B. However, in the case of the swash plate compressor disclosed in the publication No. 8-28447, the race 20b is pressed against the rollers 20c by the compression reaction force and minute dents are formed partially on the surface of the race 20b adjacent to the rollers 20c. Resistance due to such dents on the race 20b and the rolling friction of the rollers 20c cause the amorphous hard carbon film on the surface adjacent to the rollers 20c to peel off. Peeled-off film pieces present in the compressor as a foreign substance may affect various sliding portions of the compressor.
The present invention is directed to providing a swash plate compressor wherein a rolling body assembled to a swash plate through a bearing is arranged in slide contact with a shoe fitted to the piston so as to prevent the abrasion of the contact surfaces between the rolling body and the shoe and also the abrasion of the contact surfaces between the rolling body and the bearing and further to prevent peeling of the coating from the contact surfaces of the rolling body and the bearing.